This invention relates to a method of inhibiting parasitic activity by inhibiting the biosynthesis of the glycosyl phosphatidylinositol (GPI) anchor of the parasite. More particularly, the invention relates to the inhibition of parasitic activity by contacting said parasite with selected analogs of myristic acid containing various heteroatoms, substituents and unsaturated bonds.
Glycosyl phosphatidylinositols (GPIs) anchors diverse proteins to the plasma membranes of organisms ranging from the yeasts to mammals. See, e.g., the review article by Low, Biochem. J. 244, 1-13 (1987). One of the most completely characterized GPI anchors is that of the variant surface glycoprotein (VSG) of the parasitic protozoan Trypanosoma brucei. See, e.g., the research article by Ferguson et al. Science 239, 753-759 (1988), for the complete primary structure of the GPI anchors of VSG variant 117, and the review of GPI biosynthesis in T. brucei by Englund, Ann. Rev. Biochem. 62, 121-138 (1993). This parasite, in common with other African trypanosomes, evades the mammalian immune system by antigenic variation in which individual genes encoding immunologically distinct VSGs form a dense surface coat. The VSG coat acts as a macromolecular diffusion barrier which protects the parasite from lytic host-serum components.
Trypanosoma brucei is a protozoan bloodstream parasite responsible for African sleeping sickness which has a devastating effect on human health and on livestock production. Consequently, methods of inhibiting the activity of this and related protozoan parasites would have significant importance to medical science and for the development of therapeutic intervention to parasitic diseases.
Recently, in U.S. Pat. No. 5,151,445, certain myristic acid analogs have been disclosed as useful for inhibiting the growth and viability of bloodstream trypanosome parasites having a GPI membrane anchor. These analogs are oxy-substituted fatty acid analogs of C.sub.13 and C.sub.14 fatty acids or alkyl esters thereof in which a methylene group normally in carbon position from 4 to 13 of said fatty acid is replaced with oxygen. See also Doering et al., Science 252, 1851-1854 (1991).